those engineers at jpl are really good. >> landing on mars has been a tricky thing. 70% of the missions that landed on mars have failed. that's both the u.s. and with russia as well. what are the factors that complicate this? >> the atmosphere of mars is thick enough to heat your spacecraft and melt it on the way in if you don't slow down in the right way. it's thin enough that it's hard to slow down. it's a delicate balance between slowing down fast enough and not slowing down at all. that's what takes this incredibly complicated heat shield parachute rocket sky crane maneuver. >> not to mention, this is something that scientists won't be seeing in real time. there's going to be a delay. why? >> well it takes 14 minutes at this point for light to get from mars to earth. radio signals too. so this lander will be on the surface of mars in one piece or many for seven minutes before the signal gets back to earth to tell us that it's successful or not. >> we've had missions like this before. what makes this one different in. >> well this one, it's the size of a smart car in terms of weight.